Container and closure combinations presently known to the art generally consist of injection molded containers and lids wherein one or more lips or edges are molded into one component while mating grooves are molded into the other component. Locking of the closure to the container is commonly provided by diametral sizing so that the marginal edge of the lid must be stretched during engagement and the components snap into locked position. In the common arrangement, the one or more lips or edges and mating grooves require a negative draft in at least one set of molds and therefore necessitates longer chill times in the molding operation so that the material can be deformed while withdrawing the component from the mold. The degree of negative draft required is directly related to the holding power of the closure, that is, the higher the degree of negative draft and the difficulty in removing the component from the mold, the greater the security of the locking arrangement. Further, the more secure the locking arrangement the more difficult it will be for a user to remove the closure from the container. The difficulty in removing the closure is often objectionable for applications where ease of removal of the closure without the use of tools, is desirable.
In the case of containers for paint and similar substances, cylindrical metal cans have been the industry standard. While closures for these cans have been successfully designed, and the combination of can and closure or lid passes various tests, particularly the shipping drop test, the use of metal cans are objectionable both because of relatively expensive materials used therein and the inability to conveniently nest empty containers for economical shipping and storage. Attempts have been made to utilize molded plastic containers for paint and similar substances, but closures designed for such containers generally do not provide for positive locking of the closure to the container, and specifically, the combination of closure and container does not pass the test requirements, particularly the shipping drop test.
Therefore, one object of the present invention is to provide a lockable closure for a container in which the closure can be brought into and out of locking engagement with the container.
Another object of the present invention is to provide a closure which is applicable to containers of the molded plastic pail type which can be brought into and out of locking engagement with the container.
A further object of the invention is to provide a closure of simplified design producible by conventional molding methods with little or no negative draft, and which provides for locking of the closure to the container without supplemental locking means.
Still another object of the present invention is to provide a closure having means for sealing and locking the closure which does not require orientation of the closure with respect to the container.
A further object of the invention is to provide a lockable closure having self-retaining locking means which retains its unlocked or locked condition, and can be conveniently locked and unlocked by the user.
These and other objects and advantages of the present invention will be readily apparent to those skilled in the art from the following description.